FI58171C - FOERFARANDE FOER AVSKILJNING AV AONGA UR MASSA SOM KOMMER UT FRAON EN UNDER TRYCK VARANDE SKIVRAFFINOERS UTLOPPSSIDA SAMT ANORDNING FOER GENOMFOERANDE AV FOERFARANDET - Google Patents

Description

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Patent · och registerstyrelsen 7 Aimbicm utitgd och utUkrMtm pubikered 29.08.80 (32) (33) (31) PyydFtty etuollc · »» »- Begird prtorltet (71) Oy Keskuslaboratorio - Centrallaboratorium Ab, PO Box 136, FI-00101 Helsinki 10, Finland-Finland (Fl) (72) Bo Knut Mannström, Kauniainen, Suomi-Finland (FI) (7 ^) Papula Rein Lahtela Oy (5 * 0 Method for separating steam from the pulp from the outlet side of a pressurized plate refiner and equipment for carrying out the method - Förfarande för avskiljning av änga ur massa som kommer ut frän en under tryck varande skivraffinörs utloppssida samt anordning för genomförande av förfarandet

The invention relates to a method for separating steam from pressurized ground wood or pulp obtained from the outlet side of the refining chamber of a pressurized plate refiner, in which method the wood material and the steam formed during refining are removed from the refining chamber under pressure by means of an outlet conveyor. The invention further relates to an apparatus for carrying out the method, comprising an outlet conveyor tightly connected to the refining chamber of the disc refiner for removing wood and steam from the refining chamber under pressure.

The ground mass coming from the discharge side of the disc refiner contains steam generated in the grinding zone. In previously known methods, steam is separated from the ground pulp by passing the steam-mixed pulp to a cyclone separator, where the pulp is pressed down as a vortex flow and exits the lower part of the cyclone as the steam separates from the center of the flow upwards. The separated steam is discharged from the top of the cyclone at atmospheric pressure. The refiner outlet side contains a steam energy used in about 40-50% 2 581 71 grinding. However, when its pressure corresponds to atmospheric pressure, its utilization is limited. Said, previously known method and corresponding device are disclosed in Tappi, vol. 59, 1976, pp. 100-101, and J. Newell Stephenson, Preparation of Stock for Paper Making, 1965, pp. 143-144. Further, Pulp & Paper Canada, 1975, No. 12, pp. 56-57, discloses a solution for recovering steam on the feed side of a disc mill.

The method according to the present invention is characterized in that most of the wood material is removed from the discharge conveyor under pressure by means of a wood removal device before removing steam from the removal conveyor, whereby steam is removed from the discharge conveyor by a pressure removal device after removal of the wood.

Thanks to the invention the outlet side of the steam supplied from the energy is recovered in more highly valued, and energy can be utilized as paper for drying. This is very important for the energy economy. In previous methods, steam has been recovered under pressure only from the feed side of the refiner (Finnish Publication No. 51379). Approximately 40-50% of the energy used for grinding has been recovered with the steam discharged from the feed side. according to the method of the present invention, the entire system is kept under pressure and in addition to the energy contained in the feed side of said vapor is recovered even 40-50% of the energy used. Thus, it is possible to recover up to 85-90% of the energy used for grinding in the form of pressurized steam. When the amount of energy used by such a refiner is 1000-2500 kWh, 4 nons tonnes and the mass production capacity of the refiner may be 10-150 tons / day, the use of the method according to the invention means the recovery of a really considerable amount of energy.

The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 schematically shows a method and apparatus previously used, and Figure 2 schematically shows a method and apparatus according to the invention.

3,5871

According to the invention, the chips are passed between the discs of the double-disc grinder 1 by means of a screw feeder 2. The pulp is ground under pressure. The steam generated in the grinding zone between the discs, discharged on the feed side, is led to the steam outlet pipe 3 and recovered via the valve 4 under pressure, for example 1-3, preferably 1-2 bar. With the steam discharged from the feed side, 40-50% of the energy used for grinding can be recovered.

_ It is previously known (Fig. 1) to blow a pressurized, steam-containing ground mass from the discharge side of the refiner through a valve 6 at atmospheric pressure into a cyclone 7. The mass enters as a tangential flow to the top of the cyclone and continues to flow in a vortex flow down the cycle. The mass leaves the lower end of the cyclone 8.

The steam contained in the pulp is discharged from the top 9 of the cyclone. The pressure of the steam corresponds to the pressure of the surrounding atmosphere.

In the method according to the present invention (Fig. 2) the ground mass is conveyed by means of a screw conveyor 5 to a screw conveyor 10. The screw of the screw conveyor 10 preferably rotates about a vertical axis, and both the screw and the conveyor walls or at least the lower part of the screw and walls taper conically at the lower end of the screw conveyor. 11 places. The tapering of the helical conveyor 10 causes the pulp to be packed into a tight plug at the outlet end 11, whereby - steam does not escape with the pulp out of the conveyor 10. The plug forms a seal which prevents steam from escaping from the outlet end 11.

The steam contained in the pulp is led to a steam outlet pipe 12 in communication with the conveyor 10. The steam outlet pipe 12 is preferably located above the conveyor 10. Steam is recovered from the pipe 12 through the shut-off valve 13 under pressure, the overpressure is 1 to 3 bar, preferably 1-2 bar. The vertical or inclined steam tube 12 may be provided with a return screw 14 which returns any pulp particles which may be entrained with the steam back downwards. The refiner 1 and the screw conveyors 5 and 10 together form a pressurized space, the so-called the grinding chamber. Before leaving the pulp from this chamber, the steam in the pulp is almost completely separated from the solid.

58171 4

The invention is not limited to the application example presented above, but can also vary considerably within the scope of the claims. An application example relates to a double disc grinder in which the grinding is performed in one step, but the method can be applied equally well to any type of grinder. Steam extraction from the supply side can be arranged in a different way than described above.

Claims (4)

A method for separating steam from pressurized ground wood material or pulp obtained from the outlet side of the powder chamber of a pressurized disc refiner, the method comprising removing wood material and steam generated during grinding from the refining chamber under pressure by means of a pressurized outlet conveyor, characterized in ~ from the conveyor, in which case the steam is removed from the discharge conveyor also under pressure by means of a steam removal device after the removal of the wood. Method according to Claim 1, characterized in that the wood material is removed from the discharge conveyor in the form of a sealed plug. Method according to Claim 1 or 2, characterized in that the wood material which may have come from the discharge conveyor according to the steam is returned to the discharge conveyor by means of a return device. Apparatus for carrying out the method according to claim 1, comprising a discharge conveyor (5) pressure-tightly connected to the grinding chamber (1) of the disc refiner for removing wood and steam from the refining chamber under pressure, characterized in that a respectively, for removing steam from the discharge conveyor, wherein the wood removal device is connected to the discharge conveyor in front of the steam removal device and the steam removal device is connected to the discharge conveyor after the wood removal device, respectively, the movement of wood and steam is directed away from the pulp. Apparatus according to claim 3, characterized in that the wood removal device (10) consists of a helical screw conveyor which tapers towards the discharge end to remove wood from the removal conveyor (5) as a sealed plug.